ANAPHYLAXIS 247 



Besredka's theory approximates more closely. In anaphyl- 

 axis three activities come into play, the sensibilisinogen, the 

 property of serum by virtue of which it sensitizes, the 

 sensibilisin, the property due to the body and corresponding 

 to the antibody generally admitted, and the antisensibilisin, by 

 which is meant the property of normal serum in virtue of 

 which it combines with the sensibilisin and determines the 

 anaphylactic shock. 



Thus serum is toxic, not because it contains a poison ready 

 made, but because two substances, non-toxic themselves, " enter 

 into abrupt combination within the nerve-cells and thus 

 disturb their equilibrium." 



Why should small doses sensitize so well, whereas massive 

 doses only do so after a long delay ? The answer is that a 

 minute dose induces the formation of sensibilisin without 

 furnishing it with anything on which to fix : in consequence it 

 remains avid, in the nerve-cells among others. After a large 

 dose the sensibilisin manufactured is neutralized as it forms 

 by the " anti-sensibilisin " of the serum and anaphylaxis is 

 therefore delayed. It seemed probable at first that by heating 

 the serum at suitable temperatures it might be possible to 

 dissociate the two activities which do not depend on the 

 body, i.e., the sensitizing and toxic properties. But on 

 closer examination it was found that heating acted equally on 

 both ; the two in reality follow the same curve. It had also 

 to be recognized that the toxic function, the sensitizing 

 function, and the vaccinating or anti-anaphlyactic function, are 

 all fundamentally identical and occur in the same serum, but 

 that they correspond to different physical conditions of that 

 serum. 



To sensitize, a serum must be injected highly diluted ; to 

 produce the anaphylactic shock it must possess its normal 

 concentration ; to " vaccinate " or protect against the shock it 

 must unite very slowly with the sensibilisin of the body or 

 must unite with it in minute quantities at a time (e.g., in the 

 method of " continuous vaccination "). 



Heated at 100 C it is no longer toxic or very slightly 



